A turbocharger is typically used for increasing the output of an internal combustion engine through the use of energy from the exhaust gas. The turbocharger here consists of, in particular, a compressor and a turbine that are connected to each other by means of a shaft mounted in a bearing housing. During operation, the turbine is set into rotation by a flow of exhaust gas and drives the compressor by means of the shaft, wherein this compressor suctions and compresses air. The compressed air is led into the engine, wherein, due to the increased pressure during the suction cycle, a large amount of air is led into the cylinder. In this way, during each intake cycle, more oxygen is led into the combustion chamber of the engine.
Typically this leads to an increase in the maximum torque, wherein the power output, that is, the maximum output at constant working volume, is increased. This increase allows, in particular, the use of a more powerful engine with approximately the same dimensions or alternatively makes possible a reduction of the engine dimensions, that is, the realization of a comparable output for a smaller and lighter weight engine.
For effective operation of the turbocharger, the shaft and thus also the turbine and the compressor regularly rotate at high rotational speeds of, at times, up to 300,000 rpm. Especially due to the high rotational speeds, vibrations caused, for example, by the rotation of the shaft can be transmitted to the bearing unit and its individual components. To keep undesired contact with the bearing housing or individual components with each other as low as possible and to guarantee an interference-free and low-noise operation of a turbocharger, typically a bearing unit is used in which the resulting vibrations can be damped by so-called squeeze-film dampers. Normally, such a squeeze-film damper is formed essentially from an annular gap that is formed between a bearing and a bearing housing and is connected to an oil feed and is filled with a vibration-damping oil film.
Here, in particular, an outer ring of a typical roller bearing is separated from the bearing housing by a vibration-damping oil film, so that there is no direct contact between the bearing housing and outer ring. DE 10 2010 035 665 A1 describes, for example, a support for a turbocharger in which a squeeze film is present between the inner periphery of a bearing housing and the outer periphery of an outer ring of a bearing cartridge. Through such a floating bearing of the outer ring, this can be basically shifted in the axial direction. So that the bearing outer ring nevertheless always remains in the desired position and does not “slip” in the axial direction, it must be secured in the axial direction.